Detection of surface particles on chamber components with carbon dioxide

ABSTRACT

Disclosed herein is a method comprising directing, from a distribution unit, a stream comprising at least one of solid CO 2  particles or CO 2  droplets toward an article, wherein the article comprises a plurality of surface particles, and wherein the stream comprising at least one of solid CO 2  particles or CO 2  droplets causes at least a portion of the plurality of surface particles on the article to dislodge from the surface of the article; collecting, on a surface of a substrate having a pre-determined initial state comprising initial surface particles on the surface of the substrate or a real-time aerosol sampling unit, at least some of the portion of the plurality of surface particles dislodged from the surface of the article; analyzing the surface of the substrate after performing the collecting; and determining at least one of a size, a morphology, a chemical composition, a particle number concentration, or a particle size distribution of the portion of the plurality of surface particles that were dislodged from the surface of the article and collected on the surface of the substrate.

TECHNICAL FIELD

Embodiments of the present disclosure relate, in general, to detectionof surface particles of chamber components based on use of CO₂,specifically, a stream of solid CO₂ particles and/or liquid CO₂droplets.

BACKGROUND

The presence of particles on surfaces of components used inmanufacturing semiconductor devices presents a common challenge in thesemiconductor industry. A full understanding of the type of particles,as well as the quantity of particles, on the surfaces of thesecomponents can be helpful in controlling the semiconductor devicemanufacturing process. Without detecting and controlling these surfaceparticles, contamination may be introduced into a semiconductor processchamber, which could result in significant defects in a final product.For example, ceramic particles deposited on a component surface (e.g.,yttrium oxide, aluminum oxide, zirconium oxide, etc.) tend to peel offduring exposure to vacuum and plasma conditions, resulting in waferdefects and yield loss.

Standard surface particle detection methods are often ineffective indetecting a significant portion of particles on one or more surfaces ofa component. For example, liquid particle counters (LPCs) are unable todetect surface particles that are less than 100 nm in size efficiently,are unable to provide a composition of the surface particles, and arelikely to introduce cross contamination from the liquid used to analyzethe surface particles, making it difficult to obtain accurate dataregarding the surface particles. Further, LPCs are unable to target aparticular surface of a component for analysis, thus making it difficultto distinguish particles from one surface of the component. Instrumentsthat use sniffing techniques (i.e., dislodging particles from a surfaceby gentle air flow and collecting the dislodged particles for analysis)are also unable to detect surface particles that are less than 100 nm insize as the air flow used for this technique is too gentle toeffectively dislodge particles that are less than 100 nm in size.Because standard surface particle detection methods fail to provideaccurate surface particle metrology, the understanding and control ofsurface particles in the semiconductor industry is limited and asignificant number of defects may occur during the manufacturingprocess. These limitations may drive up the cost of manufacturingchamber components sometimes as much as three-fold or greater.

SUMMARY

Some of the embodiments described herein cover a method of directing,from a distribution unit, a stream of solid CO₂ particles and/or CO₂droplets toward an article, where the article includes surfaceparticles. The stream including solid CO₂ particles and/or CO₂ dropletscauses a portion of the surface particles on the article to dislodgefrom the surface of the article and become airborne. A portion of thesesurface particles may then be collected on a surface of a substratehaving a pre-determined initial state. The pre-determined initial statemay include known initial surface particles on the surface of thesubstrate. The surface of the substrate may be analyzed after performingthe collecting. A size, a morphology, a chemical composition, a particlenumber concentration, and/or a particle size distribution of the portionof surface particles that were dislodged from the surface of the articleand collected on the surface of the substrate may be determined.

In some embodiments, an apparatus includes a distribution unitconfigured to generate a stream of solid CO₂ particles or CO₂ droplets.The apparatus further includes a controller configured to direct thestream of solid CO₂ particles or CO₂ droplets toward an articleincluding surface particles, where the stream causes a portion of thesurface particles on the article to dislodge from the surface of thearticle. The apparatus also includes a substrate, having apre-determined initial state of surface particles on the surface of thesubstrate, where a surface of the substrate is to collect the portion ofsurface particles dislodged from the surface of the article. The surfaceof the article is to be analyzed to determine a size, a morphology, achemical composition, a particle number concentration, or a particlesize distribution of the portion of the surface particles that weredislodged from the surface of the article and collected on the surfaceof the substrate.

In some embodiments, an apparatus includes a distribution unitconfigured to generate a stream of solid CO₂ particles or CO₂ droplets.The apparatus further includes a controller configured to direct thestream including solid CO₂ particles or CO₂ droplets toward an articleincluding surface particles. The stream causes a portion of the surfaceparticles on the article to dislodge from the surface of the article.The apparatus also includes a real-time aerosol sampling componentconfigured to collect the surface particles dislodged from the surfaceof the article, where the collected portion of surface particles is tobe analyzed to determine, in real-time, a particle number concentration,a particle size, or a particle size distribution.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that differentreferences to “an” or “one” embodiment in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone.

FIG. 1 depicts a sectional view of a processing chamber, in accordancewith embodiments of the present disclosure.

FIG. 2 depicts an exemplary architecture of a manufacturing system, inaccordance with embodiments of the present disclosure.

FIG. 3 depicts a sectional view of a particle detection chamber, inaccordance with embodiments of the present disclosure.

FIG. 4 depicts a sectional view of a particle detection system, inaccordance with embodiments of the present disclosure.

FIG. 5 depicts a sectional view of a portable particle detection unit,in accordance with other embodiments of the present disclosure.

FIG. 6 illustrates a method for detecting and measuring particles on oneor more surfaces of an article, in accordance with embodiments of thepresent disclosure.

FIG. 7 illustrates another method for detecting and measuring particleson one or more surfaces of an article, in accordance with embodiments ofthe present disclosure.

FIG. 8 illustrates a method for dislodging particles on one or moresurfaces of an article, in accordance with embodiments of the presentdisclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments described herein relate to systems and methods fordetermining a size, a morphology, a chemical composition, a particlenumber concentration, and/or a particle size distribution of a portionof particles on a surface of an article. A stream of solid CO₂ particlesand/or liquid CO₂ droplets may be directed toward a surface of thearticle to dislodge the portion of surface particles. A portion of thedislodged surface particles may be collected by one or more surfaceparticle collection components, such as a clean substrate and/or areal-time aerosol sampling component. The collected surface particlesmay be analyzed to determine a size, a morphology, a chemicalcomposition, a particle number concentration, and/or a particle sizedistribution of the collected surface particles. Based on the analysis,information about a size, a morphology, a chemical composition, aparticle number concentration, and/or a particle size distribution maybe determined for a remainder of the surface particles on the article.

In one embodiment, liquid CO₂ may be pumped from a liquid CO₂ source,via a supply line, to a spray nozzle at a pressure of between about 400pounds per square inch (psi) to about 1,200 psi. The liquid CO₂ may beconverted into a stream of pressurized solid CO₂ particles and/or liquidCO₂ droplets as the liquid CO₂ leaves the spray nozzle. The stream ofsolid CO₂ particles and/or liquid CO₂ droplets may exit through anaperture of the spray nozzle having a diameter that is between about0.25 mm and about 1.25 mm. In some embodiments, the spray nozzle may bepositioned at a distance of about 0.25 inches to about 4 inches from thesurface of the article. In some embodiments, the spray nozzle may bepositioned and maintained at an angle of between about 15° and about 75°relative to the surface of the article. The spray nozzle may beautomatically and/or manually adjustable, so the spray nozzle is placedat an appropriate distance away from the article and at an appropriateangle relative to the surface of article. In some embodiments, the spraynozzle may be part of a hand-held CO₂ jet of a portable particledetection unit. In some embodiments, the spray nozzle is attached to arobot arm or otherwise movable assembly that may be repositioned basedon instructions from a controller.

The stream of solid CO₂ particles and/or liquid CO₂ droplets is directedtoward the article, causing at least a portion of surface particles onthe article to be dislodged. The stream of solid CO₂ particles and/orliquid CO₂ droplets may dislodge surface particles, including particlesless than 100 nm in size. In some embodiments, the surface particles mayinclude at least one of: YO—AlZr, YO—Al, YOF—AlZr, Si—YOF—AlZr, YO(Zr),AlO, YFO(Al), SiO, or YFO particles. The type of surface particles maydepend on the materials of the component at which the stream of solidCO₂ particles and/or liquid CO₂ droplets is directed.

In one embodiment, a portion of the dislodged particles may be collectedon a clean substrate. The substrate may have been previously analyzed todetermine at least a morphology, a chemical composition, a particlenumber concentration, and/or a particle size distribution of surfaceparticles on the surface of the substrate. After the portion ofdislodged particles from the article has been collected on thesubstrate, the substrate may be analyzed to determine a morphology, achemical composition, a particle number concentration, and/or a particlesize distribution of all particles on the surface of the substrate. Dataabout the initially present particles may be subtracted from the dataabout all particles subsequently present on the substrate (aftercollecting surface particles). Based on the analysis performed prior tocollecting the dislodged surface particles, and the analysis performedafter collecting the dislodged surface particles, information about amorphology, a chemical composition, a particle number concentration,and/or a particle size distribution of the remainder of surfaceparticles on the article can be determined. This information can be usedto determine whether further cleaning of the article should be performedbefore the article is used in a manufacturing process or to root causeparticles excursion.

The portion of the dislodged particles may additionally or alternativelybe collected by a real-time aerosol sampling component. The real-timeaerosol sampling component may be an optical particle counter, a laserparticle counter, an aerodynamic particle sizer, a condensation particlecounter, or an ultrafine condensation particle counter. In someembodiments, the real-time aerosol sampling component may havedetermined a particle number concentration, a particle size, and/or aparticle size distribution for one or more particles of the particledetection system (referred to herein as background particles) prior tocollecting the dislodged surface particles. After the portion ofdislodged particles have been collected by the aerosol samplingcomponent, a particle number concentration, a particle size, and/or aparticle size distribution may be determined, in real-time, for allparticles detected by the aerosol sampling component (i.e., backgroundparticles and collected dislodged particles). Based on the analysisperformed prior to collecting the dislodged surface particles, and theanalysis performed after collecting the dislodged surface particles,information about the particle number concentration, the particle size,and/or the particle size distribution for the remainder of surfaceparticles on the article can be determined. In some embodiments, thesubstrate and the real-time aerosol sampling component may be used inparallel to analyze the dislodged surface particles.

In some embodiments, a laminar flow may be provided within the particledetection system to facilitate the transport of dislodged surfaceparticles from the article to the one or more surface particle detectioncomponents. The laminar flow may be generated by providing air from anexterior of the particle detection system through a flow straightenerprovided at an inlet of the particle detection system. In someembodiments, a pre-filter and/or a high efficiency particulate airfilter may be provided along with the flow straightener to removeparticles from the exterior air source that may interfere with thedetection of the dislodged surface particles by the surface particledetection components. In some embodiments, one or more particle chargeneutralizers may be provided within the particle detection system toreduce an amount of charge carried by the dislodged surface particlesbeing transported to the surface particle detection components.

It may be advantageous to detect particles on the surface of an articleto determine whether, before the article is used in a manufacturingprocess, further processing and/or cleaning of the article is needed. Asize, a morphology, a chemical composition, a particle numberconcentration, and/or a particle size distribution of the particles onthe surface of the article may indicate additional processing and/orcleaning steps to be performed, before using the article in themanufacturing process. It may be advantageous to use a stream of solidCO₂ particles and/or liquid CO₂ droplets to dislodge particles from oneor more surfaces of the article. The stream of solid CO₂ particlesand/or liquid CO₂ droplets improves the detection of surface particlesas the CO₂ stream dislodges small particles on the surface of thearticle, including particles smaller than 100 nm in size. By dislodgingparticles smaller than 100 nm in size from the surface of the article,an accurate size, morphology, chemical composition, particle numberconcentration, and/or particle size distribution of the particles on thesurface of the article may be determined. It may be further advantageousto use the stream of solid CO₂ particles and/or liquid CO₂ droplets todislodge the surface particles as the CO₂ stream may not interfere witha functionality of the article. Further, the CO₂ stream may be directedto select portions of a surface of the article, so to determine a size,a morphology, a chemical composition, a particle number concentration,and/or a particle size distribution of a select portion of the surfacerather than the entire surface of the article. Such information mayindicate whether a targeted processing and/or cleaning step may beperformed prior to using the article in the manufacturing process.

Embodiments are discussed with regards to the detection of surfaceparticles attached or deposited on a surface of a chamber component.However, it should be understood that embodiments described herein alsoapply to the detection of surface particles deposited on a surface ofother manufactured components.

FIG. 1 depicts a sectional view of a processing chamber 100, inaccordance with embodiments of the present disclosure. The processingchamber 100 may be used for processes in which a corrosive plasmaenvironment is provided. For example, the processing chamber 100 may bea chamber for a plasma etcher or plasma etch reactor, a plasma cleaner,and so forth. In alternative embodiments other processing chambers maybe used, which may or may not be exposed to a corrosive plasmaenvironment. Some examples of chamber components include a chemicalvapor deposition (CVD) chamber, a physical vapor deposition (PVD)chamber, an atomic layer deposition (ALD) chamber, an ion assisteddeposition (IAD) chamber, an etch chamber, and other types of processingchambers.

Examples of chamber components that may be analyzed for surfaceparticles according to embodiments described herein include, but are notlimited to, a substrate support assembly 148, an electrostatic chuck(ESC) 150, a gas distribution plate, a nozzle, a showerhead, a flowequalizer, a cooling base, a gas feeder, a chamber lid, a liner, a ring,a view port, and so on. Embodiments may be used with chamber componentsthat include one or more apertures as well as with chamber componentsthat do not include any apertures. The chamber component may be aceramic article having a compositing of at least one of Al₂O₃, AlN,SiO₂, Y₃Al₅O₁₂, Y₄Al₂O₉, Y₂O₃, Er₂O₃, Gd₂O₃, Gd₃Al₅O₁₂, YF₃, Nd₂O₃,Er₄Al₂O₉, Er₃Al₅O₁₂, ErAlO₃, Gd₄Al₂O₉, GdAlO₃, Nd₃Al₅O₁₂, Nd₄Al₂O₉,NdAlO₃, or a ceramic compound composed of Y₄Al₂O₉ and a solid-solutionof Y₂O₃—ZrO₂. Alternatively, the chamber component may be anotherceramic, may be a metal (e.g., Al, stainless steel, etc.), or a metalalloy. The chamber component may also include both a ceramic portion anda non-ceramic (e.g., metal) portion.

In one embodiment, the processing chamber 100 includes a chamber body102 and a showerhead 130 that encloses an interior volume 106. Theshowerhead 130 may include a showerhead base and a showerhead gasdistribution plate. Alternatively, the showerhead 130 may be replaced bya lid and a nozzle in some embodiments, or by multiple pie shapedshowerhead compartments and plasma generation units in otherembodiments. The chamber body 102 may be fabricated from aluminum,stainless steel or other suitable material such as titanium (Ti). Thechamber body 102 generally includes sidewalls 108 and a bottom 110.

An outer liner 116 may be disposed adjacent the sidewalls 108 to protectthe chamber body 102. The outer liner 116 may be fabricated to includeone or more apertures. In one embodiment, the outer liner 116 isfabricated from aluminum oxide.

An exhaust port 126 may be defined in the chamber body 102, and maycouple the interior volume 106 to a pump system 128. The pump system 128may include one or more pumps and throttle valves utilized to evacuateand regulate the pressure of the interior volume 106 of the processingchamber 100.

The showerhead 130 may be supported on the sidewall 108 of the chamberbody 102. The showerhead 130 (or lid) may be opened to allow access tothe interior volume 106 of the processing chamber 100, and may provide aseal for the processing chamber 100 while closed. A gas panel 158 may becoupled to the processing chamber 100 to provide process and/or cleaninggases to the interior volume 106 through the showerhead 130 or lid andnozzle (e.g., through apertures of the showerhead or lid and nozzle).Showerhead 130 may be used for processing chambers used for dielectricetch (etching of dielectric materials). The showerhead 130 may include agas distribution plate (GDP) and may have multiple gas delivery holes132 (also referred to as channels) throughout the GDP. The showerhead130 may be formed by metal or alloy plate with the protection by amulti-layer protective coating as described herein. The metal or alloyplate may be composed of aluminum, an aluminum alloy, or another metalor metal alloy. The showerhead 130 may be formed with the GDP bonded toan aluminum base or an anodized aluminum base. The GDP may be made fromSi or SiC, or may be a ceramic such as Y₂O₃, Al₂O₃, Y₃Al₅O₁₂ (YAG), andso forth.

For processing chambers used for conductor etch (etching of conductivematerials), a lid may be used rather than a showerhead. The lid mayinclude a center nozzle that fits into a center hole of the lid. The lidmay be a ceramic such as Al₂O₃, Y₂O₃, YAG, or a ceramic compoundincluding Y₄Al₂O₉ and a solid-solution of Y₂O₃—ZrO₂. The nozzle may alsobe a ceramic, such as Y₂O₃, YAG, or the ceramic compound includingY₄Al₂O₉ and a solid-solution of Y₂O₃—ZrO₂.

Examples of processing gases that may be used to process substrates inthe processing chamber 100 include halogen-containing gases, such asC₂F₆, SF₆, SiCl₄, HBr, NF₃, CF₄, CHF₃, CH₂F₃, F, NF₃, Cl₂, CCl₄, BCl₃and SiF₄, among others, and other gases such as O₂, or N₂O. A remoteplasma may be formed from any of these and/or other processing gases andthen delivered through the plasma delivery line 112 to chamber 100.Accordingly, the remote plasma may be composed of C₂F₆, SF₆, SiCl₄, HBr,NF₃, CF₄, CHF₃, CH₂F₃, F, NF₃, Cl₂, CCl₄, BCl₃ and SiF₄, among others,and other gases such as O₂, or N₂O. Examples of carrier gases includeN₂, He, Ar, and other gases inert to process gases (e.g., non-reactivegases).

A substrate support assembly 148 is disposed in the interior volume 106of the processing chamber 100 below the showerhead 130. The substratesupport assembly 148 holds a substrate 144 during processing. A ring(e.g., a single ring) may cover a portion of the electrostatic chuck150, and may protect the covered portion from exposure to plasma duringprocessing. The ring may be silicon or quartz in one embodiment.

An inner liner may be coated on the periphery of the substrate supportassembly 148. The inner liner may be a halogen-containing gas resistmaterial such as those discussed with reference to the outer liner 116.In one embodiment, the inner liner may be fabricated from the samematerials of the outer liner 116.

In one embodiment, the substrate support assembly 148 includes apedestal 152 that supports an electrostatic chuck 150. The electrostaticchuck 150 further includes a thermally conductive base and anelectrostatic puck bonded to the thermally conductive base by a bond,which may be a silicone bond in one embodiment. The thermally conductivebase and/or electrostatic puck of the electrostatic chuck 150 mayinclude one or more optional embedded heating elements, embedded thermalisolators and/or conduits to control a lateral temperature profile ofthe substrate support assembly 148. The electrostatic puck may furtherinclude multiple gas passages such as grooves, mesas and other surfacefeatures that may be formed in an upper surface of the electrostaticpuck. The gas passages may be fluidly coupled to a source of a heattransfer (or backside) gas such as He via holes drilled in theelectrostatic puck. In operation, the backside gas may be provided atcontrolled pressure into the gas passages to enhance the heat transferbetween the electrostatic puck and a supported substrate 144. Theelectrostatic chuck 150 may include at least one clamping electrodecontrolled by a chucking power source.

FIG. 2 depicts an exemplary architecture of a manufacturing system 200,in accordance with embodiments of the present disclosure. Manufacturingsystem 200 may be a ceramics manufacturing system, which may includeprocessing chamber 100. Manufacturing system 200 may further include aparticle detection system 205, an equipment automation layer 215, and acomputing device 220. In alternative embodiments, manufacturing system200 may include more or fewer components. For example, manufacturingsystem 200 may include only particle detection system 205, which may bea manual off-line machine.

Particle detection system 205 may be a machine designed to direct astream of solid CO₂ particles and/or CO₂ droplets toward one or moresurfaces of an article (e.g., a ceramic article for use in asemiconductor processing chamber). Particle detection system 205 mayinclude an adjustable article support assembly used to hold the articlein place as the stream of solid CO₂ particles and/or CO₂ droplets aredirected toward the article. Particle detection system 205 may alsoinclude a store of liquid CO₂ and a distribution unit, such as a spraynozzle, for generating the solid CO₂ particles and/or liquid CO₂droplets from the liquid CO₂. Further details with respect to particledetection system 205 are provided herein.

Particle detection system 205 may be an off-line machine that can beprogrammed with a process recipe (e.g., using a programmablecontroller). The process recipe may control an orientation of thearticle, CO₂ pressure in the distribution unit, orientation of thedistribution unit with respect to the article, process time durations,article temperature and/or chamber temperature, or any other suitableparameter. Each process parameter will be discussed in greater detailherein. Alternatively, particle detection system 205 may be an on-lineautomated machine that can receive process recipes from computingdevices 220 (e.g., personal computers, server machines, etc.) viaequipment automation layer 215. The equipment automation layer 215 mayinterconnect particle detection system 205 with computing devices 220,with other manufacturing machines, with metrology tools, and/or otherdevices.

Equipment automation layer 215 may include a network (e.g., a locationarea network (LAN)), routers, gateways, servers, data stores, and so on.Particle detection system 205 may connect to equipment automation layer215 via a SEMI Equipment Communications Standard/Generic Equipment Model(SECS/GEM) interface, via an Ethernet interface, and/or via otherinterfaces. In one embodiment, equipment automation layer 215 enablesprocess data to be stored in a data store (not shown). In an alternativeembodiment, computing device 220 connects directly to particle detectionsystem 205.

In one embodiment, particle detection system 205 may include aprogrammable controller that can load, store, and execute processprotocols. The programmable controller may control pressure settings,fluid flow settings, time settings, etc., for a process performed byparticle detection system 205. The programmable controller may include amain memory (e.g., read-only memory (ROM), flash memory, dynamic randomaccess memory (DRAM), static random access memory (SRAM), etc.), and/ora secondary memory (e.g., a data storage device such as a disk drive).The main memory and/or secondary memory may store instructions fordetecting surface particles on a surface of an article, as describedherein.

The programmable controller may also include a processing device coupledto the main memory and/or secondary memory (e.g., via a bus) to executethe instructions. The processing device may be a general-purposeprocessing device such as a microprocessor, central processing unit, orthe like. The processing device may also be a special-purpose processingdevice, such as an application specific integrated circuit (ASIC), afield programmable gate array (FPGA), a digital signal processor (DSP),a network processor, or the like. In one embodiment, programmablecontroller is a programmable logic controller (PLC).

FIG. 3 depicts a sectional view of an exemplary particle detectionchamber 300, in accordance with embodiments of the present disclosure.For example, the particle detection chamber 300 may be the same orsimilar to particle detection system 205 described with respect to FIG.2. Particle detection chamber 300 may be configured to dislodge aportion of particles from at least one surface of an article 302.Article 302 may be any suitable chamber component described with respectto FIG. 1, including a substrate support assembly, an electrostaticchuck (ESC), a chamber wall, a base, a nozzle, a gas distribution plateor showerhead, a liner, a liner kit, a shield, a plasma screen, a flowequalizer, a cooling base, a chamber lid, etc. Article 302 may be aceramic material, metal-ceramic composite, or a polymer-ceramiccomposite. Article 302 may have any suitable dimensions forincorporation into a semiconductor chamber. In some embodiments, article302 may be a newly fabricated chamber component that has not been coatedor otherwise processed. In other embodiments, article 302 may be acoated chamber component or may be a used chamber component.

Article 302 may be supported within particle detection chamber 300 by anarticle support assembly 304. Article support assembly 304 may beautomatically and/or manually adjustable to position article 302 duringthe particle detection process, and may be capable of rotating, tilting,and/or translating article 302 in three dimensions. In some embodiments,article support assembly 304 may be operatively coupled to aprogrammable controller (not shown), described with respect to FIG. 2.The programmable controller may store one or more process recipesassociated with the particle detection process. Each process recipe mayinclude execution protocols relating to an orientation of articlesupport assembly 304. During the particle detection process, theprogrammable controller may cause article support assembly 304 to berotated, tilted, and/or translated according to one or more executionprotocols of a process recipe.

In some embodiments, article support assembly 304 may be a perforatedplate or a mesh screen that is configured to support article 302 withinparticle detection system 300. The perforated plate or the mesh screenmay be made of stainless steel or polytetrafluoroethene (i.e., Teflon)in some embodiments. Particles that are dislodged from a surface ofarticle 302 may pass through the perforated plate or mesh screen duringthe particle detection process. In other embodiments, article supportassembly 304 may include one or more grips (not shown) where each gripis configured to contact surfaces of article 302 to prevent article 302from slipping. The grips may be applied to article 302 with enough forceto firmly hold article 302 in place while also minimizing the contactarea with article 302. In some embodiments, article support assembly 304may include one or more heating elements which may be activated tocontrol a temperature of article 302.

Particle detection chamber 300 may also include a distribution unit,such as spray nozzle 306. Spray nozzle 306 may be fluidly coupled to aliquid CO₂ source 308 via a supply line 310. Supply line 310 may includeone or more valves for controlling the liquid CO₂ being provided tospray nozzle 306. Additionally, a pump (not shown) may be used to pumpliquid CO₂ from liquid CO₂ source 308 through spray nozzle 306 and tocontrol the pressure of the liquid CO₂.

Liquid CO₂ may be pumped from liquid CO₂ source 308 through spray nozzle306 and directed to a portion of a surface of article 302. As liquid CO₂exits spray nozzle 306, the liquid CO₂ may be converted to a stream 312of solid CO₂ particles and/or liquid CO₂ droplets (herein referred to asa CO₂ stream) directed toward article 302. In some embodiments, theliquid CO₂ may be supplied to spray nozzle 306 at a pressure betweenabout 400 psi to about 1,200 psi. In one embodiment, liquid CO₂ may besupplied to spray nozzle 306 at a pressure of between about 700 psi toabout 900 psi. In some embodiments, spray nozzle 306 may be a throttlingnozzle, which causes an isenthalpic expansion of the liquid CO₂, suchthat when the CO₂ exits nozzle 306, it expands into the CO₂ stream 312.In some embodiments, CO₂ stream 312 exits through an aperture of spraynozzle 306 having a diameter that between about 0.25 mm and about 1.25mm. In one embodiment, the aperture of spray nozzle 306 may have adiameter of less than 1 mm.

Without being bound by theory, it is believed that the solid CO₂particles and liquid CO₂ droplets strike surface particles on surfacesof article 302, transferring momentum to the surface particles, causingthe surface particles to be dislodged from the surfaces of article 302.In some embodiments, the stream path is oriented at an angle withrespect to a surface of article 302, which may provide higher momentumto the surface particles while minimizing damage to article 302 than mayoccur from orienting the stream path directly toward article 302. In oneembodiment, the angle may be between about 15° and about 75°.

Spray nozzle 306 may be positioned and maintained at a distance of about0.25 inches to about 4 inches from a surface of article 302. In oneembodiment, spray nozzle 306 may be positioned and maintained at adistance of about 0.5 inches to about 2 inches from the surface ofarticle 302. Spray nozzle 306 may be automatically and/or manuallyadjustable such that spray nozzle 306 is placed at an appropriatedistance away from article 302 and at an appropriate angle relative tothe surface of article 302. In some embodiments, spray nozzle 306 may beoperatively coupled to the programmable controller, where one or moreprocess recipes stored by the programmable controller include executionprotocols relating to an orientation of spray nozzle 306. In oneembodiment, programmable controller may cause spray nozzle 306 to betranslated toward or away from article 302, and the angle relative tothe surface of article 302 to be increased or decreased, according toone or more execution protocols of a process recipe. Alternatively, oradditionally, the orientation of spray nozzle 306 and article supportassembly 304 may be adjusted in coordination during the particledetection process, according to one or more execution protocols of aprocess recipe.

In some embodiments, the liquid CO₂ may pass through a fine mesh filter314 (e.g., a nickel mesh filter) to remove gross particulates (i.e., CO₂particles having a size greater than a spacing of the mesh) from theliquid CO₂ source 308 and/or supply line 310 prior to exiting spraynozzle 306. The fine mesh filter 314 may be positioned at an input ofnozzle 306, at an output of nozzle 306, or at an intermediate positionwithin nozzle 306.

Spray nozzle 306 may be configured to direct CO₂ stream 312 towardarticle 302 in either a spraying mode or a scanning mode. Spraying modemay include a continuous spraying mode and/or a pulsing spraying mode.Scanning mode may include a point scanning mode and/or an area scanmode. During the continuous spraying mode, CO₂ stream 312 may bedirected toward article 302 continuously for a first period of time,until a first layer of solid CO₂ has formed on a surface of article 302.The first solid CO₂ layer may cause a temperature of article 302 todecrease. During the first time period, a portion of the surfaceparticles may be dislodged from the surface of article 302. After thefirst solid CO₂ layer has formed and the portion of surface particleshave dislodged, a recovery time period (i.e., a second period of time)may be given to allow the first solid CO₂ layer to sublimate (i.e.,transition from a solid phase to a gas phase) and the temperature ofarticle 302 to increase. In some embodiments, a temperature of a laminarflow 316 provided within particle detection chamber 300 (described infurther detail herein) may be increased to facilitate the increase ofthe temperature of article 302. In other embodiments, a heating elementincluded in article support assembly 304 may be activated to facilitatethe increase of the temperature of article 302. After the first solidCO₂ layer has sublimated and the temperature of article 302 hasincreased to a threshold temperature, CO₂ stream 312 may be directedtoward article 302 continuously for a third period of time, until asecond layer of solid CO₂ has formed on a surface of article 302. Thesecond solid CO₂ layer may cause a portion of the surface particles todislodge from the surface of article 302. Another recovery time period(i.e., a fourth period of time) may be given to allow the second solidCO₂ layer to sublimate and the temperature of article 302 to increase.The above described process (formation of solid CO₂ layer andsublimation) may be performed repeatedly in some embodiments (e.g.,until a threshold number of surface particles remain on the surface ofarticle 302). The number of surface particles on the surface of article302 may be measured after the formation of a solid CO₂ layer, inaccordance with embodiments described herein.

During the pulsing spraying mode, spray nozzle 306 may be turned on andoff periodically with a consistent frequency until it is determined(e.g., by a real-time aerosol sampling component described in furtherdetail herein), that a threshold number of particles have dislodged fromthe surface of article 302. In some embodiments, a solid CO₂ layer mayform on the surface of article 302 during the pulsing spraying mode.

As discussed previously, CO₂ stream 312 may also be directed in either apoint scanning mode or an area scanning mode. During the point scanningmode, spray nozzle 306 may be fixed within particle detection system 300and targeted to a single portion of a surface of article 302. Particleswithin the single portion may be dislodged from the surface and analyzedby at least a real-time aerosol sampling instrument 332 to determine atleast a particle number concentration, particle size, and/or a particlesize distribution of the dislodged particles. The position of spraynozzle 306 relative to the surface of article 302 may change to targetdifferent portions on the surface of article 302 during the particledetection process and the dislodged particles from each targeted portionmay be analyzed. By targeting different portions of article 302, a levelof surface cleanliness for various spots on the surface of article 302may be determined.

During the area scanning mode, the position of spray nozzle 306,relative to a surface of article 302, may continuously change as CO₂stream 312 is directed toward article 302. In some embodiments, theposition of spray nozzle 306 may be changed in a continuous line or acircular pattern on the surface of article 302 at a constant velocity.In one embodiment, the constant velocity may be between about 0.25inch/s to about 2 inch/s. The dislodged surface particles may becollected and analyzed by at least a real-time aerosol samplinginstrument 332 to determine at least a particle number concentration,particle size, and/or particle size distribution of the dislodgedsurface particles. By continuously changing the area of the surface ofarticle 302 targeted by spray nozzle 306, an averaged article surfacecleanliness may be determined.

To prevent dislodged surface particles from re-depositing on a surfaceof article 302, or from depositing on one or more inner walls ofparticle detection chamber 300, a laminar flow 316 may be providedwithin particle detection chamber 300. Laminar flow 316 may be generatedby providing air from an exterior of particle detection chamber 300(referred to herein as carrier air) through a flow straightener 318provided at an inlet of particle detection chamber 300. In someembodiments, flow straightener 318 may be a honeycomb or a wovenstainless steel plate. Laminar flow 316 may be provided through flowstraightener 318 at a velocity of between about 0.5 m/s to about 1 m/s.Laminar flow 316 may be provided at the inlet of particle detectionchamber 300 and transport dislodged surface particles toward an outlet320 of particle detection chamber 300. In some embodiments a pre-filter322 may be provided along with flow straightener 318 to remove particlesfrom the carrier air that may interfere with the detection of surfaceparticles dislodged from a surface of article 302 (referred to herein asbackground particles). Additionally, a high efficiency particulate airfilter 324 may be provided along with flow straightener 318 to removeadditional background particles that were not removed by pre-filter 322.In some embodiments, both pre-filter 322 and particulate air filter 324may be provided upstream from flow straightener 318. In otherembodiments, pre-filter 322 may be provided upstream from flowstraightener 318 and particulate air filter 324 may be provideddownstream from flow straightener 318.

One or more particle charge neutralizers 326 may be provided withinparticle detection chamber 300 to reduce an amount of charge carried bydislodged surface particles, thereby reducing particle transport lossdue to electrostatic attraction. In some embodiments, particle chargeneutralizers 326 may be a radioactive source, such as one or morePolonium-210 strips. Particle charge neutralizers may be placed on oneor more inner walls of particle detection chamber 300 and may reduce anamount of charge carried by dislodged surface particles as the dislodgedsurface particles are being transported, by laminar flow 316 towardoutlet 320.

A substrate 328 may be provided below article 302 (as illustrated), oron a side of particle detection chamber 300 close to article 302, tocollect a sample of dislodged surface particles transported from article302 toward outlet 320. Substrate 328 may be supported by substratesupport assembly 330. Substrate support assembly 330 may be the same asarticle support assembly 304. Substrate 328 may be any clean surfaceconfigured to collect a sample of dislodged surface particles fromarticle 302. In some embodiments, substrate 328 may be a clean waferthat has a diameter of 300 mm or smaller.

A surface of substrate 328 may be analyzed, prior to collecting aportion of dislodged surface particles, to determine a morphology, achemical composition, a particle number concentration, and/or a particlesize distribution of surface particles on the surface of substrate 328.After substrate 328 has collected at least a portion of dislodgedsurface particles from article 302, substrate 328 may be analyzed todetermine a size, a morphology, a chemical composition, a particlenumber concentration, and/or a particle size distribution of allparticles on the surface of substrate 328. Based on the analysisperformed prior to collecting the dislodged surface particles, and theanalysis performed after collecting the dislodged surface particles, asize, a morphology, a chemical composition, a particle numberconcentration, a particle size distribution, and/or a total particlecount may be of substrate 328 may be determined for the surfaceparticles remaining on article 302 after the particle detection processis complete. Such determination may provide a quantitative indication ofa cleanliness of a surface of article 302. In some embodiments,substrate 328 may be analyzed by various metrologies, such as scanningelectron microscope (SEM)/energy-dispersive X-ray (EDX) metrology. Inother embodiments, substrate 328 may be analyzed by a surface scanningmetrology apparatus, such as SurfScan® metrology, manufactured by KLACorporation, to determine a particle size and total particle count forsurface particles on substrate 328.

In some embodiments, particle detection chamber 300 may further includea real-time aerosol sampling component 332. Real-time aerosol samplingcomponent 332 may be provided in parallel with substrate 328, or insteadof substrate 328. Aerosol sampling component 332 may be configured tocollect at least a portion of dislodged surface particles from a surfaceof article 302 and determine, in real time, a particle numberconcentration, a particle size and/or a particle size distribution ofthe portion of collected dislodged surface particles. Aerosol samplingcomponent 332 may collect and analyze a portion of background particleswithin particle detection system 300 prior to collecting and analyzingthe portion of dislodged surface particles from the surface of article302. Aerosol sampling component 332 may then collect and analyze theportion of dislodged surface particles from article 302. Based on theanalysis performed prior to collecting the dislodged surface particles,and the analysis performed after collecting the dislodged surfaceparticles, a particle number concentration, a particle size, and/or aparticle size distribution may be determined for the remainder ofsurface particles on article 302.

Aerosol sampling component 332 may include at least one of an opticalparticle counter, a laser particle counter, an aerodynamic particlesizer, a condensation particle counter, or an ultrafine condensationparticle counter. In some embodiments, a cascade impactor may beprovided in addition to, or instead of, aerosol sampling component 332to collect dislodged surface particle samples for further analysis(e.g., by SEM/EDX metrology). In some embodiments, a velocity of laminarflow 316 may be adjusted to correspond with a sampling flow velocity ofaerosol sampling component 332 such to achieve isokinetic sampling viaan aerosol sampling probe 334.

An aerosol sampling probe 334 may be provided as part of aerosolsampling component 332 to collect at least a portion of dislodgedsurface particles transported from article 302. In some embodiments,aerosol sampling probe 334 may be connected to an aerosol samplinginstrument of aerosol sampling component via a tubing. The tubing mayhave a length of between about 2 inches and 5 inches in someembodiments. In some embodiments, the tubing should be as short aspossible to reduce particle transport loss between aerosol samplingprobe 334 and the aerosol sampling instrument. The tubing may becomposed of a metal, such as stainless steel or Tygon, to reduce surfaceparticle transport loss.

After the dislodged particles are collected by substrate 328 and/oraerosol sampling component 332 and analyzed in accordance withpreviously described embodiments (i.e., a particle detection cycle iscomplete), particle detection chamber 300 may be purged to remove atleast a portion of dislodged surface particles and/or backgroundparticles remaining within the interior of particle detection chamber300. In some embodiments, particle detection chamber 300 may be purgedusing aggressive filtered clean dry air (CDA). One or more CDA nozzles336 provided within particle detection chamber 300 may be targetedtoward an inner wall of particle detection chamber 300. CDA may beprovided by CDA nozzles 336 to remove any dislodged surface particlesthat were deposited on an inner wall of particle detection chamber 300,as well as any background particles remaining from a previous particledetection cycle.

In some embodiments, a velocity of laminar flow 316 may also beincreased significantly to facilitate dislodging and transport ofsurface and/or background particles deposited on an inner wall ofparticle detection chamber 300. In one embodiment, the velocity oflaminar flow 316 may be increased to 10 m/s. Aerosol sampling component332 may collect at least a portion of particles being purged fromparticle detection chamber 300 and determine, in real-time, at least aparticle number concentration of the collected particles.

In some embodiments, a high flow, low flow purge cycle may be performedto purge particles from particle detection chamber 300. In a high flow,low flow purge cycle, the velocity of laminar flow 316 may be increased(e.g., to 10 m/s or higher) within particle deposition chamber 300 for afirst period of time (referred to herein as a high flow period). Afteran expiration of the first period of time, the velocity of laminar flow316 may be decreased (e.g., to approximately 1 m/s) for a second periodof time (referred to herein as a low flow period). Aerosol samplingcomponent 332 may collect at least a portion of particles being purgedduring the first period of time and the second period of time anddetermine, in real-time, at least a particle number concentration of thecollected particles. The high flow period and the low flow period may berepeated until the particle concentration determined by aerosol samplingcomponent 332 falls below a threshold particle concentration (e.g., 1particle/cm3). In some embodiments, CDA may be provided by CDA nozzles336 during the high flow period and the low flow period.

After extensive use of particle detection chamber 300, a particleconcentration determined by aerosol sampling component 332 may not fallbelow a threshold particle concentration by purging particle detectionchamber 300, in accordance with previously described embodiments. Insome embodiments, one or more inner wall surfaces of particle detectionchamber 300 may be cleaned using an isopropyl alcohol (IPA) solution toremove at least a portion of particles deposited on the inner wallsurfaces. In one embodiment, a 9% IPA solution may be wiped onto thesurface of one or more inner walls to remove at least a portion of theparticles. In some embodiments, article support assembly 304 maysimilarly be cleaned using an IPA solution to remove at least a portionof particles deposited on one or more surfaces of article supportassembly 304. In other embodiments, article support assembly 304 may beremoved from particle detection chamber 300 and cleaned by anultrasonicated deionized water bath.

FIG. 4 depicts a sectional view of another particle detection system400, in accordance with embodiments of the present disclosure. Particledetection system 400 may be the same or similar to particle detectionsystem 205 described with respect to FIG. 2. Particle detection system400 may be configured to dislodge at least a portion of surfaceparticles from at least one surface of an article 402. Article 402 maybe any suitable chamber component described with respect to FIG. 1 andFIG. 3.

In some embodiments, particle detection system 400 may include a systembody 404, in which article 402 may be provided within system body 404.In some embodiments, system body 404 may be a small, stainless steelfixture, such as a cylindrical stainless steel cup. System body 404 maybe configured such to maintain a fixed distance between a distributionunit, such as spray nozzle 408, and article 402. As described withrespect to FIG. 3, spray nozzle 408 may be fluidly coupled to a liquidCO₂ source (not shown) via a supply line (not shown). A pump (not shown)may be used to pump liquid CO₂ from the liquid CO₂ source through spraynozzle 408 and to control a pressure of the liquid CO₂. As liquid CO₂exits spray nozzle 408, the liquid CO₂ may be converted to a CO₂ stream410 (i.e., a stream of solid CO₂ particles and/or liquid CO₂ droplets)directed toward article 402. In some embodiments, the fixed distancebetween spray nozzle 408 and article 402 may depend on a pressure(and/or a flow rate) of CO₂ stream 410. For example, if CO₂ stream 410is being directed toward article 402 at a pressure of between about 400psi to about 1,200 psi, the fixed distance between spray nozzle 408 andarticle 402 may be between about 0.25 inches and 4 inches.

Article 402 may be supported within particle detection system 400 by asupport assembly 412. Support assembly may be fixed within particledetection system 400. In some embodiments, support assembly 412 may be aperforated plate or a mesh screen that is configured to support article402 at the fixed distance between spray nozzle 408 and article 402. Insuch embodiments, support assembly 412 may prevent positive pressurebuildup within particle detection system 400. In one embodiment, supportassembly 412 may be made of stainless steel. Surface particles that aredislodged from a surface of article 402 may pass through supportassembly 412 during the particle detection process. In otherembodiments, support assembly 412 may include one or more grips (notshown), as previously described with respect to FIG. 3.

A substrate 414 may be provided below article 402 to collect a sample ofsurface particles dislodged from a surface of article 402. In someembodiments, substrate 414 may be displaced at the bottom of particledetection system 400. In other embodiments, substrate 414 may besupported by a substrate support assembly (not shown). Substrate 414 maybe any clean surface configured to collect a sample of dislodged surfaceparticles. In some embodiments, substrate 414 may be a clean wafer thathas a diameter of 300 nm or smaller. In some embodiments, substrate 414may be analyzed prior to collecting the portion of dislodged surfaceparticles to determine a morphology, a chemical composition, a particlenumber concentration, and/or a particle size distribution of allbackground particles deposited on substrate 414. Responsive tocollecting the portion of dislodged surface particles, substrate 414 maybe analyzed to determine a size, a morphology, a chemical composition, aparticle number concentration, and/or a particle size distribution ofall particles on the surface of substrate 414. Based on the analysisperformed prior to the collection of dislodged surface particles, andthe analysis performed after the collection of dislodged surfaceparticles, a size, a morphology, a chemical composition, a particlenumber concentration, and/or a particle size distribution may bedetermined for all dislodged surface particles collected by substrate414.

In some embodiments, CO₂ stream 410 may cause turbulent flow 416 withinparticle detection system 400. Turbulent flow 416 may facilitate thetransport of the dislodged particles (which may become airborne) fromthe surface of article 402 to substrate 414. Turbulent flow 416 may alsoensure the dislodged surface particles are mixed thoroughly insidesystem body 404. In some embodiments system body 404 may include one ormore openings 418, where the interior of system body 404 is exposed tothe exterior system body 404. Openings 418 may minimize positivepressure buildup inside system body 404 caused by turbulent flow 416.

In some embodiments, a real-time aerosol sampling component 420 may beprovided within particle detection system 400. Aerosol samplingcomponent 420 may be configured to collect at least a portion ofdislodged surface particles from a surface of article 402 and determine,in real time, a particle number concentration, a particle size and/or aparticle size distribution of the portion of collected dislodged surfaceparticles. Aerosol sampling component 420 may include at least one of anoptical particle counter, a laser particle counter, an aerodynamicparticle sizer, a condensation particle counter, or an ultrafinecondensation particle counter

FIG. 5 depicts a sectional view of a portable particle detection unit500, in accordance with other embodiments of the present disclosure. Theportable particle detection unit 500 may be the same or similar toparticle detection 205 described with respect to FIG. 2. Portableparticle detection unit 500 may be configured to dislodge at least aportion of surface particles from at least one surface of an article502. Article 502 may be any suitable chamber component described withrespect to FIG. 1 and FIG. 3.

Portable particle detection unit 500 may include a hand-held CO₂ jet504. Hand-held CO₂ jet 504 may include a distribution unit, such asspray nozzle 506, and a handle 508. As described with respect to FIG. 3,spray nozzle 506 may be fluidly coupled to a liquid CO₂ source 510 via asupply line 512. In some embodiments, liquid CO₂ source 510 may be atank filled with compressed CO₂. In other embodiments, liquid CO₂ source308 may be a portable CO₂ container. Liquid CO₂ may be pumped fromliquid CO₂ source 510 through spray nozzle 506. As liquid CO₂ exitsspray nozzle 506, the liquid CO₂ may be converted to a CO₂ stream 514(i.e., a stream of solid CO₂ particles and/or liquid CO₂ droplets)directed toward article 502. An operator may use handle 508 to movehand-held CO₂ jet 504 in relation to article 502. The operator may usehandle 508 to control the distance between spray nozzle 506 and article502, the angle that CO₂ stream 514 is being directed toward article 502,and/or a portion of article 502 in which CO₂ stream 514 is directed. CO₂stream 514 may cause at least a portion of surface particles on article502 to be dislodged from at least one surface.

A substrate 516 may be configured with respect to article 502 such thatsubstrate 516 is to collect at least a portion of dislodged surfaceparticles from one or more surfaces of article 502. Article 502 may beangled such that, when CO₂ stream 514 is directed toward article 502, aportion of surface particles dislodged from a surface of article 502 maybe transported toward substrate 516 by gravitational force. In someembodiments, substrate 516 may be analyzed prior to collecting theportion of dislodged surface particles to determine a morphology, achemical composition, a particle number concentration, and/or a particlesize distribution of all background particles deposited on substrate516. Responsive to collecting the portion of dislodged surfaceparticles, substrate 516 may be analyzed to determine a size, amorphology, a chemical composition, a particle number concentration,and/or a particle size distribution of all particles on the surface ofsubstrate 516. Based on the analysis performed prior to the collectionof dislodged surface particles, and the analysis performed after thecollection of dislodged surface particles, a size, a morphology, achemical composition, a particle number concentration, and/or a particlesize distribution may be determined for all dislodged surface particlescollected by substrate 516.

FIG. 6 illustrates a method 600 for detecting and measuring particles onone or more surfaces of an article, in accordance with embodiments ofthe present disclosure. At block 610, a size, a morphology, a chemicalcomposition, a particle number concentration, and/or a particle sizedistribution of surface particles on a surface of a substrate may bedetermined. In some embodiments, the substrate may be analyzed byvarious metrologies, such as SEM/EDX metrology, or by a surface scanningmetrology apparatus to determine a particle size and total particlecount on the substrate. A size, a morphology, a chemical composition, aparticle number concentration, and/or a particle size distribution ofsurface particles on the surface of the substrate may be determinedprior to collecting dislodged surface particles from one or moresurfaces of an article so to identify characteristics associated withparticles present within the particle detection system (i.e., backgroundparticles) prior to initiation of the surface particle collectionprocess.

At block 620, the substrate and an article including surface particlesis provided to a particle detection system. In some embodiments, theparticle detection system may be particle detection chamber 300 of FIG.3, particle detection system 400 of FIG. 4, or portable particledetection unit 500 of FIG. 5. The article may be supported within theparticle detection system by an article support assembly, while thesubstrate may be supported by a substrate support assembly. The articlesupport assembly may be automatically and/or manually adjustable toposition the article during the particle detection process, and may becapable of rotating, tilting, or translating the article in threedimensions. The substrate may be provided within the particle detectionsystem so to collect a sample of surface particles dislodged from asurface of the article (i.e., below the article, as illustrated in FIG.3, on a side of the particle detection system, etc.).

At block 630, a stream of solid CO₂ particles and/or CO₂ droplets (CO₂stream) is directed toward the article, causing a portion of surfaceparticles to dislodge from the surface of the article. The CO₂ streammay be provided by a distribution unit, such as a spray nozzle, withinthe particle detection system that is configured to direct the CO₂stream toward a surface of the article. The distribution unit may befluidly coupled to a liquid CO₂ source via a supply line, where theliquid CO₂ may be pumped from the liquid CO₂ source through thedistribution unit and be converted into the CO₂ stream. The CO₂ streammay cause a portion of the surface particles to be dislodged from thesurface of the article be transported to the substrate.

At block 640, a laminar flow may be generated around the surface of thearticle to facilitate transportation of the dislodged surface particlesto the substrate. The laminar flow may be generated by providing carrierair through a flow straightener provided at an inlet of the particledetection system. In some embodiments, the carrier air is passed througha pre-filter provided along with the flow straightener at the inlet ofthe particle detection system to remove background particles from thecarrier air. In one embodiment, a high efficiency particulate air filtermay also be provided with the flow straightener to remove additionalparticles that were not removed by the pre-filter. In some embodiments,one or more particle charge neutralizers may be provided within theparticle detection system to remove an amount of charge carried bydislodged surface particles, thereby reducing particle transport lossdue to electrostatic attraction.

At block 650, a portion of the surface particles dislodged from thesurface of the article is collected on the surface of the substrate. Atblock 660, the surface of the substrate is analyzed to determine a size,a morphology, a chemical composition, a particle number concentration,and/or a particle size distribution of all particles on the surface ofthe substrate. In some embodiments, the substrate may be analyzed byvarious metrologies, such as SEM/EDX metrology. In other embodiments, aparticle size and total particle count on the substrate may be analyzedby a surface scanning metrology apparatus.

At block 670, a size, a morphology, a chemical composition, a particlenumber concentration, and/or a particle size distribution of thedislodged surface particles collected on the surface of the substrate isdetermined. These particle properties may be determined using any of theaforementioned metrology devices and/or techniques. The size,morphology, chemical composition, particle number concentration, and/orparticle size distribution may be determined by subtracting thecorresponding values determined at block 610 from the correspondingvalues of the analysis performed at block 660. By subtracting the valuesof block 610 from the values of block 660, a remainder is determined,which indicates a size, a morphology, a chemical composition, a particlenumber concentration, and/or a particle size distribution of thedislodged surface particles collected by the substrate.

In some embodiments, a real-time aerosol sampling component may beprovided in parallel with the substrate. The aerosol sampling componentmay collect a portion of dislodged surface particles and determine, inreal time, a particle number concentration, a particle size, and/or aparticle size distribution of the dislodged surface particles.

At block 680, the particle detection system may be purged to dislodgethe surface particles redeposited on one or more inner walls of theparticle detection chamber after the CO₂ stream was directed toward thesurface of the article. In some embodiments, the particle detectionsystem may be purged using aggressive filtered CDA. One or more CDAnozzles may be provided within the particle detection system may betargeted toward an inner wall of the particle detection system and mayprovide CDA to remove a portion of the redeposited surface particles. Insome embodiments, a velocity of the laminar flow described with respectto block 640 may be increased significantly to facilitate dislodging andtransport of the redeposited surface particles on the inner wall of theparticle detection system. In some embodiments, after one or moreparticle detection cycles, one or more inner wall surfaces of theparticle detection system, and/or the article support assembly, may becleaned using an IPA solution to remove at least a portion ofredeposited particles, in accordance with previously describedembodiments.

FIG. 7 illustrates a method 700 for detecting and measuring surfaceparticles from a surface of an article, in accordance with embodimentsof the present disclosure. At block 710, a particle numberconcentration, a particle size, and/or a particle size distribution forbackground particles in a particle detection system is determined usinga real-time aerosol sampling component. The aerosol sampling componentmay be configured to collect a portion of background particles anddetermine, in real time, a particle number concentration, a particlesize and/or a particle size distribution of the portion of the collectedbackground particles. The aerosol sampling component may include atleast one of an optical particle counter, a laser particle counter, anaerodynamic particle sizer, a condensation particle counter, or anultrafine condensation particle counter

At block 720, an article is provided to the particle detection system.In some embodiments, the particle detection system may be particledetection chamber 300 of FIG. 3 or particle detection system 400 of FIG.4. The article may be supported within the particle detection system byan article support assembly. The article support assembly may beautomatically and/or manually adjustable to position the article duringthe particle detection process, and may be capable of rotating, tilting,or translating the article in three dimensions.

At block 730, a stream of solid CO₂ particles and/or CO₂ droplets (CO₂stream) is directed toward the article, causing a portion surfaceparticles to dislodge from a surface of the article. The CO₂ stream maybe provided by a distribution unit, such as a spray nozzle, within theparticle detection system that is configured to direct the CO₂ streamtoward a surface of the article. The distribution unit may be fluidlycoupled to a liquid CO₂ source via a supply line, where the liquid CO₂may be pumped form the liquid CO₂ source through the distribution unitand converted into the CO₂ stream. The CO₂ stream may cause a portionsurface particles to be dislodged from the surface of the article andtransported to the aerosol sampling component. At block 740, a laminarflow may be generated around the article to transport the portion ofsurface particles dislodged from the surface of the article to theaerosol sampling component. In some embodiments, one or more particlecharge neutralizers provided within the particle detection system mayremove an amount of charge carried by dislodged surface particles,thereby reducing particle transport loss due to electrostaticattraction.

At block 750, a portion dislodged surface particles is collected by theaerosol sampling component. The aerosol sampling component maydetermine, in real time, a particle number concentration, a particlesize and/or a particle size distribution of the portion of collecteddislodged surface particles.

At block 760, a particle number concentration, a particle size, and/or aparticle size distribution for dislodged surface particles collected bythe aerosol sampling component is determined. The particle numberconcentration, particle size, and/or particle size distribution may bedetermined by subtracting the corresponding values determined at block710 from the corresponding values of the analysis performed at block750. By subtracting the values of block 710 from the values of block750, a remainder is determined, which indicates a size, a morphology, achemical composition, a particle number concentration, and/or a particlesize distribution of the dislodged surface particles dislodged collectedby the aerosol sampling component.

At block 770, the particle detection chamber may be purged to dislodgesurface particles were redeposited on one or more inner walls of theparticle detection chamber after the CO₂ stream was directed toward thesurface of the article. In some embodiments, the particle detectionsystem may be purged using aggressive filtered CDA. One or more CDAnozzles may be provided within the particle detection system may betargeted toward an inner wall of the particle detection system and mayprovide CDA to remove a portion of the redeposited surface particles. Insome embodiments, a velocity of the laminar flow described with respectto block 740 may be increased significantly to facilitate dislodging andtransport of the redeposited surface particles on the inner wall of theparticle detection system. In some embodiments, after one or moreparticle detection cycles, one or more inner wall surfaces of theparticle detection system, and/or the article support assembly, may becleaned using an IPA solution to remove a portion of redeposited surfaceparticles, in accordance with previously described embodiments.

FIG. 8 illustrates a method 800 for dislodging particles on one or moresurfaces of an article, in accordance with embodiments of the presentdisclosure. At block 810, a stream of solid CO₂ particles and/or CO₂droplets (CO₂ stream) is directed toward the article, causing a portionof surface particles to dislodge from the surface of the article. TheCO₂ stream may be provided by a distribution unit, such as a spraynozzle, within the particle detection system that is configured todirect the CO₂ stream toward the article, in accordance with embodimentspreviously described herein. A first solid layer of CO₂ may form on thesurface of the article. The CO₂ stream may cause a portion of surfaceparticles to be dislodged from the surface of the article.

At block 820, the portion of dislodged surface particles is collected bya real-time aerosol sampling component. The aerosol sampling componentmay include at least one of an optical particle counter, a laserparticle counter, an aerodynamic particle sizer, a condensation particlecounter, or an ultrafine condensation particle counter. At block 830, aparticle number concentration for the dislodged surface particlescollected by the aerosol sampling component is determined, in accordancewith embodiments previously described herein. At block 840, it isdetermined whether the particle number concentration exceeds a thresholdparticle number concentration. In some embodiments, the thresholdparticle number concentration may be 1 particle/cm³.

Responsive to determining that the particle number concentration exceedsa threshold particle number concentration, method 800 may continue toblock 850, where a temperature of the article is increased to facilitatesublimation of the first solid CO₂ layer on the surface of the article.In some embodiments, the temperature of the article may be increased byincreasing a temperature of the article support assembly. In otherembodiments, the temperature of the article may be increased byincreasing a temperature of the laminar flow. After the first solid CO₂layer on the surface of the article has sublimated, method 800 mayreturn to block 810, where a second CO₂ stream is directed toward thesurface of the article to form a second solid CO₂ layer on the surfaceof the article, causing a second portion of surface particles to bedislodged. Responsive to determining that the particle numberconcentration does not exceed a threshold particle number concentration,method 800 may terminate.

The preceding description sets forth numerous specific details such asexamples of specific systems, components, methods, and so forth in orderto provide a good understanding of several embodiments of the presentdisclosure. It will be apparent to one skilled in the art, however, thatat least some embodiments of the present disclosure may be practicedwithout these specific details. In other instances, well-knowncomponents or methods are not described in detail or are presented insimple block diagram format in order to avoid unnecessarily obscuringthe present disclosure. Thus, the specific details set forth are merelyexemplary. Particular implementations may vary from these exemplarydetails and still be contemplated to be within the scope of the presentdisclosure.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment” in various places throughout thisspecification are not necessarily all referring to the same embodiment.In addition, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or.” When the term “about” or “approximately” is usedherein, this is intended to mean that the nominal value presented isprecise within ±10%.

Although the operations of the methods herein are shown and described ina particular order, the order of operations of each method may bealtered so that certain operations may be performed in an inverse orderso that certain operations may be performed, at least in part,concurrently with other operations. In another embodiment, instructionsor sub-operations of distinct operations may be in an intermittentand/or alternating manner.

It is understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. The scope of the disclosure should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

What is claimed is:
 1. A method comprising: directing, from adistribution unit, a stream comprising at least one of solid CO₂particles or CO₂ droplets toward an article, wherein the articlecomprises a plurality of surface particles, and wherein the streamcomprising at least one of solid CO₂ particles or CO₂ droplets causes atleast a portion of the plurality of surface particles on the article todislodge from a surface of the article; collecting, on a surface of asubstrate having a pre-determined initial state comprising initialsurface particles on the surface of the substrate, at least some of theportion of the plurality of surface particles dislodged from the surfaceof the article; analyzing the surface of the substrate after performingthe collecting; and determining at least one of a size, a morphology, achemical composition, a particle number concentration, or a particlesize distribution of the portion of the plurality of surface particlesthat were dislodged from the surface of the article and collected on thesurface of the substrate.
 2. The method of claim 1, further comprising:determining information about at least one of a size, a morphology, achemical composition, a particle number concentration, or a particlesize distribution of a remainder of the plurality of surface particleson the article.
 3. The method of claim 1, further comprising:determining at least one of a size, a morphology, a chemicalcomposition, a particle number concentration, or a particle sizedistribution of all detectable surface particles on the substrate; andsubtracting out at least one of a size, a morphology, a chemicalcomposition, a particle number concentration, or a particle sizedistribution of pre-determined particles included in the pre-determinedinitial state; wherein a remainder of at least one of the size, themorphology, the chemical composition, the particle number concentration,or the particle size distribution of all detectable surface particles onthe substrate represents data for the portion of the plurality ofsurface particles that were dislodged from the surface of the articleand collected on the surface of the substrate.
 4. The method of claim 1,further comprising: generating a laminar flow around the article totransport the portion of the plurality of surface particles dislodgedfrom the surface of the article to the substrate.
 5. The method of claim1, further comprising: reducing, by one or more particle chargeneutralizers, a charge of the portion of the plurality of surfaceparticles dislodged from the surface of the article such to facilitatetransport to the substrate.
 6. The method of claim 1, wherein directingthe stream comprising at least one of solid CO₂ particles or CO₂droplets toward the article comprises: forming a first layer of solidCO₂ on the surface of the article, wherein the first layer of solid CO₂causes the portion of the plurality of surface particles to be dislodgedfrom the surface of the article, and wherein at least a portion of thedislodged surface particles are to collect on the surface of thearticle; increasing a temperature of the article to facilitatesublimation of the first layer of solid CO₂; and forming a second layerof solid CO₂ on the surface of the article, wherein the second layer ofsolid CO₂ causes the portion of the dislodged surface particles to bedislodged from the surface of the article.
 7. The method of claim 1,wherein directing the stream comprising at least one of solid CO₂particles or CO₂ droplets towards the article comprises: flowing liquidCO₂ into the distribution unit, wherein the liquid CO₂ is converted intoat least one of solid CO₂ particles or CO₂ droplets upon exiting thedistribution unit.
 8. An apparatus comprising: a distribution unitconfigured to generate a stream comprising at least one of solid CO₂particles or CO₂ droplets; a controller configured to direct the streamcomprising at least one of solid CO₂ particles or CO₂ droplets toward anarticle comprising a plurality of surface particles, wherein the streamcauses at least a portion of the plurality of surface particles on thearticle to dislodge from a surface of the article; and a substratehaving a pre-determined initial state comprising surface particles on asurface of the substrate, wherein a surface of the substrate is tocollect the portion of the plurality of surface particles dislodged fromthe surface of the article, and wherein the surface of the substrate isto be analyzed to determine at least one of a size, a morphology, achemical composition, a particle number concentration, or a particlesize distribution of the portion of the plurality of surface particlesthat were dislodged from the surface of the article and collected on thesurface of the substrate.
 9. The apparatus of claim 8, whereininformation about at least one of a size, a morphology, a chemicalcomposition, a particle number concentration, or a particle sizedistribution of a remainder of the plurality of surface particles on thearticle is determined based on a determination of at least one of asize, a morphology, a chemical composition, a particle numberconcentration, or a particle size distribution of the portion of theplurality of surface particles that were dislodged from the surface ofthe article and collected on the surface of the substrate
 10. Theapparatus of claim 8, further comprising a laminar flow componentconfigured to generate a laminar flow around the article to transportthe portion of the plurality of surface particles that were dislodgedfrom the surface of the article to the substrate.
 11. The apparatus ofclaim 8, further comprising one or more particle charge neutralizersconfigured to reduce a charge of the portion of the plurality of surfaceparticles that were dislodged from the surface of the article such tofacilitate transport to the substrate.
 12. The apparatus of claim 8,further comprising a liquid CO₂ source fluidly coupled to thedistribution unit, wherein liquid CO₂ is configured to flow from theliquid CO₂ source into the distribution unit such that the liquid CO₂ isconverted into at least one of solid CO₂ particles or CO₂ droplets uponexiting the distribution unit.
 13. The apparatus of claim 8, wherein thecontroller is further configured to: direct a first stream comprising atleast one of solid CO₂ particles or CO₂ droplets toward the article fora first time period, wherein the first stream causes a first layer ofsolid CO₂ to be formed on the article, and wherein the first layer ofsolid CO₂ causes the portion of the plurality of surface particles to bedislodged from the surface of the article, and wherein at least aportion of the dislodged surface particles are to collect on the surfaceof the article; stop the first stream for a second time period duringwhich a temperature of the article is increased to facilitatesublimation of the first layer of solid CO₂ on the surface of thearticle; and direct a second stream comprising at least one of solid CO₂particles or CO₂ droplets toward the article for a third time period,wherein the second stream causes a second layer of solid CO₂ to beformed on the article, and wherein the second layer of solid CO₂ causesthe portion of the dislodged surface particles to be dislodged from thesurface of the article.
 14. An apparatus comprising: a distribution unitconfigured to generate a stream comprising at least one of solid CO₂particles or CO₂ droplets; a controller configured to direct the streamcomprising at least one of solid CO₂ particles or CO₂ droplets toward anarticle comprising a plurality of surface particles, wherein the streamcauses at least a portion of the plurality of surface particles on thearticle to dislodge from a surface of the article; and a real-timeaerosol sampling component configured to collect the portion of theplurality of surface particles dislodged from the surface of thearticle, wherein the collected portion surface particles is to beanalyzed to determine, in real-time, at least one of a particle numberconcentration, a particle size, or a particle size distribution.
 15. Theapparatus of claim 14, wherein information about at least one of a size,a particle number concentration, a particle size, or a particle sizedistribution of a remainder of the plurality of surface particles on thearticle is determined based on a determination of at least one of aparticle number concentration, a particle size, or a particle sizedistribution of the portion of the plurality of surface particles thatwere dislodged from the surface of the article and collected by thereal-time aerosol sampling component.
 16. The apparatus of claim 14,further comprising a laminar flow component configured to generate alaminar flow around the article to transport the portion of theplurality of surface particles that were dislodged from the surface ofthe article to the real-time aerosol sampling component.
 17. Theapparatus of claim 14, further comprising one or more particle chargeneutralizers configured to reduce a charge of the portion of theplurality of surface particles that were dislodged from the surface ofthe article such to facilitate transport to the real-time aerosolsampling component.
 18. The apparatus of claim 14, further comprising aliquid CO₂ source fluidly coupled to the distribution unit, whereinliquid CO₂ is configured to flow from the liquid CO₂ source into thedistribution unit such that the liquid CO₂ is converted into at leastone of solid CO₂ particles or CO₂ droplets upon exiting the distributionunit.
 19. The apparatus of claim 14, wherein the controller is furtherconfigured to: direct a first stream comprising at least one of solidCO₂ particles or CO₂ droplets toward the article for a first timeperiod, wherein the first stream causes a first layer of solid CO₂ to beformed on the article, and wherein the first layer of solid CO₂ causesthe portion of the plurality of surface particles to be dislodged fromthe surface of the article, and wherein at least a portion of thedislodged surface particles are to collect on the surface of thearticle; stop the first stream for a second time period during which atemperature of the article is increased to facilitate sublimation of thefirst layer of solid CO₂ on the surface of the article; and direct asecond stream comprising at least one of solid CO₂ particles or CO₂droplets toward the article for a third time period, wherein the secondstream causes a second layer of solid CO₂ to be formed on the article,and wherein the second layer of solid CO₂ causes the portion of thedislodged surface particles to be dislodged from the surface of thearticle.
 20. The apparatus of claim 14, wherein the real-time aerosolsampling component comprises at least one of a laser particle counter,an aerodynamic particle sizer, a condensation particle counter, or anultrafine condensation particle counter.